If one and a half boys, eat one and a half burgers in one and a half hours. How many burgers can 9 boys eat in 3 hours?

Question

A pipe can fill a tank in 8 hours.
A fter 3/5 of the tank is filled, four more pipes of half capacity is opened to fill the tank.
What is the total time taken to completely fill the tank?

Answer 1

I think answer is 18
=2*6*1.5 = 18

Answer 2

The answer is 18. The boys are increased by 6 times and the time twice .Therefore,the burger is increased 12 times.The answer is 12*1.5=18